Extract a thumbnail from a camera JPEG file using libexif

exif_example.cpp

#include <stdio.h>
#include <libexif/exif-loader.h>

// Note: no error handling and no cleanup for clarity.
int main()
{
  ExifLoader *loader = exif_loader_new();
  exif_loader_write_file(loader, "IMG_20170422_132409.jpg");
  ExifData *ed = exif_loader_get_data(loader);
  ed = exif_loader_get_data(loader);
  if (ed && ed->data && ed->size) {
    fwrite(ed->data, 1, ed->size, fopen("thumb.jpg", "wb"));
  }
}